Can you build a better brain with blueberries – or with fish, walnuts or kale?

The idea that certain super foods can keep us sharper as we age has huge appeal – especially as study after study suggests that brain power will not be found in a supplement pill. The latest, published in August in the medical journal JAMA, showed that older adults who took nutritional supplements, including omega-3 fatty acids (found in fatty fish and walnuts) and a combo of lutein and zeaxanthin (found in leafy greens), experienced just as much cognitive decline over a five-year period as those who took placebo pills.

The results "were not at all surprising," given previous similar findings, says Sudeep Gill, an associate professor of geriatric medicine at Queen's University, Kingston, Ontario. But, as Gill and colleague Dallas Seitz wrote in an editorial accompanying the JAMA study, the disappointing results on supplements do not mean nutrition doesn't matter to brain health.

In fact, quite a few studies suggest that certain diets – often the same diets that are good for our hearts – can help slow memory loss and other signs of brain aging. Such diets might even help prevent Alzheimer's disease. And they may well contain lots of blueberries, fish, walnuts and kale – though the evidence for particular foods tends to be spottier than the evidence for broader eating patterns, researchers say.

"People don't just eat individual things," says Alain Koyama, a researcher at the San Francisco VA Medical Center. "It's more realistic to look at dietary patterns."

Among those promising eating patterns:

• The Mediterranean diet. This is a diet that includes lots of fruits, vegetables, whole grains, nuts and legumes, plus olive oil and, often, wine. Some versions call for fish several times a week. In several observational studies – the kind where researchers just look at what people already eat, rather than assign diets to them – people whose diets are closest to the Mediterranean pattern show lower rates of cognitive decline. A recent study that assigned the diet, plus extra olive oil or nuts, to some older adults in Spain found that they held onto their cognitive abilities more firmly than adults assigned a different diet.

• The DASH diet. That stands for Dietary Approaches to Stop Hypertension and, as the name implies, it can lower blood pressure. But observational studies show people who eat DASH-like diets also show slower rates of cognitive decline. The diet limits salt, sweets and red meat and includes lots of fruits, vegetables, nuts, legumes and whole grains, plus low-fat dairy. In one study designed to study heart health, people assigned to the DASH diet appeared to get some cognitive benefits.

• The MIND diet. This diet takes elements of the Mediterranean and DASH diets and puts additional emphasis on foods that show particular brain-boosting promise. Those include leafy greens, nuts and berries. In observational studies, the MIND diet was associated with reduced risks of cognitive decline and Alzheimer's disease. The diet does not require as much fish as the Mediterranean diet or as many fruit and vegetable servings as the DASH diet and is generally "not as strict," says Martha Morris, a nutritional epidemiologist at Rush University Medical Center, Chicago.

Despite such promising leads, the science on diet and brain aging remains "too inconclusive to warrant recommendations for dietary change," an expert committee convened by the Institute of Medicine wrote recently. The committee did say the evidence "provides some justification for individual choices to eat less meat and more nuts and legumes, whole grains, and monounsaturated fats, such as olive oil, to preserve cognitive health."

Heidi Wengreen, an assistant professor of nutrition at Utah State University, agrees that many questions remain, but says: "We have a lot of good clues and we have a lot of common elements."

Exactly why some eating patterns might be good for the brain is not clear. One key may be that diets that keep blood flowing to the heart also keep it flowing to the brain. Also, certain nutrients may help prevent inflammation in the brain or otherwise protect brain cells, Wengreen says.

While getting those nutrients in a supplement might make sense for some people who do not get enough through diet, she says, the real money is on real food: "There's probably a synergistic effect from the nutrients found in whole foods that you just can't get when you take a supplement."

And there's little downside – except the costs of some of the foods -- to adopting the most promising eating patterns, because they are in line with current dietary guidelines, Gill says.